Perhaps the most immediate opportunity for saving fuel - and therefore cutting emissions - is by changing the way planes are flown and directed once airborne. Air traffic controllers in Europe believe that up to 12% of the global fleet's current fuel burn could be saved simply by making planes fly more direct routes. For example, London-Bangkok routes fly around the Himalayas as well as make other diversions to avoid costly overflight charges that some countries demand. More "point-to-point" flights (A-B flights) and less "hub-and-spoke" routes (A-B, but via C) could minimise fuel wastage, too.

Also, there are 36 national air traffic authorities in Europe. This complexity leads to a 7% inefficiency when just a 1% saving could save up to 500,000 tonnes of fuel a year, according to Eurocontrol, Europe's agency for the safety of air navigation. One fully centralised system could also reduce wasteful "stacking" as planes back-up in the air due to delays.

Landing

When a plane touches down, its reverse thrusters use a lot of fuel bringing it to an abrupt but controlled halt. Parachutes or spoilers could be used instead, as could greater use of the runway's length. Many airports now insist on a "controlled descent approach" to reduce noise. More use of this landing technique - which prevents sharply curved approaches - would also use less fuel as the plane "glides" in to land.

Aerodynamics

A 1% reduction in drag leads to a 1.1% reduction in fuel burn. Winglets (up-turned wing tips) and other leading-edge innovations are being introduced.

Capacity

Flying more people in less planes is one of Airbus's boasts for its new giant A380. Business class is also a wasteful use of space. This is partly why easyJet claims it is more "environmentally friendly" than, say, BA. EasyJet planes carry 156 people at full capacity - introducing business class would reduce this to 110 or 120. Standing areas for short flights are also being discussed in the industry.

Weight

The next generation of planes, such as the Boeing 787 Dreamliner, are partly constructed out of lighter composite materials to help reduce weight. TAP Portugal has even stopped handing out newspapers to help reduce weight.

Fuel cells

Both Boeing and Airbus are soon set to start trials using hydrogen fuel cells to generate onboard electrical power instead of the traditional kerosene-powered auxiliary power units usually found in the tail of a plane.